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Register a new userMeasurement of branching fractions, isospin and CP-violating asymmetries for exclusive boldmath$b to dgamma$ modes
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We report new measurements of the decays $Btorho^+ gamma$, $B to rho^0 gamma$ and $B to omegagamma$ using a data sample of $657 times 10^6$ $B$ meson pairs accumulated with the Belle detector at the KEKB $e^+ e^-$ collider. We measure branching fractions ${cal B}(B^+ to rho^+ gamma) = (8.7^{+2.9}_{-2.7}{}^{+0.9}_{-1.1})times 10^{-7}$, ${cal B}(B^0 to rho^0 gamma) = (7.8^{+1.7}_{-1.6}{}^{+0.9}_{-1.0}) times 10^{-7}$ and ${cal B}(B^0 to omega gamma) = (4.0^{+1.9}_{-1.7} pm 1.3) times 10^{-7}$. We also report the isospin asymmetry $Delta (rhogamma) = -0.48^{+0.21}_{-0.19}{}^{+0.08}_{-0.09}$; and the first measurement of the direct CP-violating asymmetry $A_{CP}(B^+ to rho^+ gamma) = -0.11pm{0.32}pm{0.09}$, where the first and second errors are statistical and systematic, respectively.
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The isospin asymmetries of $B to Kmu^+mu^-$ and $B to K^{*}mu^+mu^-$ decays and the partial branching fractions of the $B^0 to K^0mu^+mu^-$, $B^+ to K^+mu^+mu^-$ and $B^+ to K^{*+}mu^+mu^-$ decays are measured as functions of the dimuon mass squared, $q^2$. The data used correspond to an integrated luminosity of 3$~$fb$^{-1}$ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7$,$TeV and 8$,$TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions, while individually consistent, all favour lower values than their respective Standard Model predictions.
We report measurements of branching fractions and time-dependent CP asymmetries in $B^{0} to D^{+}D^{-}$ and $B^{0} to D^{*pm}D^{mp}$ decays using a data sample that contains $(772 pm 11)times 10^6 Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We determine the branching fractions to be $mathcal{B}(B^{0} to D^{+}D^{-})=(2.12 pm 0.16 pm 0.18)times 10^{-4}$ and $mathcal{B}(B^{0} to D^{*pm}D^{mp}=(6.14 pm 0.29 pm 0.50)times 10^{-4}$. We measure CP asymmetry parameters $mathcal{S}_{D^{+}D^{-}} = -1.06_{-0.14}^{+0.21} pm 0.08$ and $mathcal{C}_{D^{+}D^{-}} = -0.43 pm 0.16 pm 0.05$ in $B^{0} to D^{+}D^{-}$ and $mathcal{A}_{D^{*}D} = +0.06 pm 0.05 pm 0.02$, $mathcal{S}_{D^{*}D} = -0.78 pm 0.15 pm 0.05$, $mathcal{C}_{D^{*}D} = -0.01 pm 0.11 pm 0.04$, $Deltamathcal{S}_{D^{*}D} = -0.13 pm 0.15 pm 0.04$ and $Deltamathcal{C}_{D^{*}D} = +0.12 pm 0.11 pm 0.03$ in $B^{0} to D^{*pm}D^{mp}$, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of CP symmetry in both decays at equal to or greater than $4sigma$ significance.
We report measurements of the branching fractions and direct CP asymmetries (A_{CP}) for B->K pi, pi pi and KK decays (but not pi^0 pi^0) based on the final data sample of 772x10^6 B B-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We set a 90% confidence-level upper limit for K^+- K^-+ at 2.0x10^{-7}; all other decays are observed with branching fractions ranging from 10^{-6} to 10^{-5}. In the $B^0/B^0-bar -> K^+-pi^-+ mode, we confirm Belles previously reported large A_{CP} with a value of -0.069 +- 0.014 +- 0.007 and a significance of 4.4 sigma. For all other flavor-specific modes, we find A_{CP} values consistent with zero, including A_{CP}(K^+- pi^0) = +0.043 +- 0.024 +- 0.007 with 1.8 sigma significance. The difference of CP asymmetry between B^+- -> K^+- pi^0 and B^0/B^0-bar -> K^+-pi^-+ is found to be Delta A_{K pi} equiv A_{CP} (K^+ pi^0) - A_{CP}(K^+ pi^-) = +0.112 +- 0.027 +- 0.007 with 4.0 sigma significance. We also calculate the ratios of partial widths for the B-> K pi decays. Using our results, we test the validity of the sum rule A_{CP}(K^+ pi^-) + A_{CP}(K^0pi^+) x Gamma(K^0pi^+)/Gamma(K^+ pi^-)} - A_{CP}(K^+ pi^0)x 2Gamma(K^+ pi^0)/Gamma(K^+ pi^-) - A_{CP}(K^0 pi^0)x 2Gamma(K^0 pi^0)/Gamma(K^+ pi^-) = 0 and obtain a sum of -0.270 +- 0.132 +- 0.060 with 1.9 sigma significance.
The ratio of branching fractions and the difference in $CP$ asymmetries of the decays $B^+to J/psi pi^+$ and $B^+to J/psi K^+$ are measured using a data sample of $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of $3~{{,mbox{fb}^{-1}}}$ at centre-of-mass energies of 7 and $8~mathrm{,Tekern -0.1em V}$. The results are begin{equation*} {mathcal{B}(B^+to J/psi pi^+)overmathcal{B}(B^+to J/psi K^+)}=(3.83pm0.03pm0.03)times10^{-2},, end{equation*} begin{equation*} mathcal{A}^{CP}(B^+to J/psi pi^+)-mathcal{A}^{CP}(B^+to J/psi K^+)=(1.82pm0.86pm0.14)times10^{-2}, end{equation*} where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of $mathcal{A}^{CP}(B^+to J/psi K^+)$ provides the most precise estimate to date of $CP$ violation in the decay $B^+to J/psi pi^+$, begin{equation*} mathcal{A}^{CP}(B^+to J/psi pi^+) =(1.91pm0.89pm0.16)times10^{-2}. end{equation*}
We report on first measurements of branching fractions~($mathcal{B}$) and CP-violating charge asymmetries~($mathcal{A}$) in charmless $B$ decays at Belle~II. We use a sample of electron-positron collisions collected in 2019 and 2020 at the $Upsilon(4S)$ resonance and corresponding to $34.6$,fb$^{-1}$ of integrated luminosity. We use simulation to determine optimized event selections. The $Delta E$ distributions of the resulting samples, restricted in $M_{rm bc}$, are fit to determine signal yields. Signal yields are corrected for efficiencies determined from simulation and control data samples to obtain branching fractions and CP-violating asymmetries for flavour-specific channels. These are the first measurements in charmless decays reported by Belle~II. Results are compatible with known determinations and show detector performance comparable with the best Belle results offering a reliable basis to assess projections for future reach.
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